The problem of finding the optimal set of causal pixels (support) for
use in linear predictive models is addressed. After presenting counter
examples to popular intuitions about supports, a general result relati
ng the distortion incurred with a small support to optimal coefficient
s of a larger support is derived. A geometrical interpretation is prov
ided. Two algorithms that optimally increase/decrease support sizes by
one at each step are presented, Experimental results illustrate the s
ignificant gains realized by the algorithms compared with commonly use
d supports.